                1. Field of the Invention        
The present invention relates to the mounting of jet engines onto an aircraft structure.                2. Description of the Related Art        
A jet engine, such as a turbojet engine, may be mounted at various points of the aircraft being hung from a mast or pylon that is part of the aircraft structure. It may be mounted under the wings, attached to the fuselage, generally at the rear, or mounted in the tail unit by mounting means. The function of these mounting means is to ensure the transmission of mechanical loads between the engine and the aircraft structure. The loads to be taken into consideration are oriented along the three main directions of a reference frame related to the engine. These are the weight of the engine along the vertical axis Z, its thrust along axis X of the engine, and lateral aerodynamic loads along the transverse axis Y. The loads to be transmitted also comprise the rotational torque about the engine axis. These means must also absorb the deformations undergone by the engine during the different flight phases, without transmitting the same to the pylon, which are derived for example from dimensional variations due to thermal expansions or contractions.
The connection between the engine and the pylon is generally ensured, for turbofan jet engines, by two mounts, one forward of the engine and the other aft. Each of the mounting means is arranged to transmit part of the loads. For example, one of the mounts ensures the transmission of lateral forces along axis Y and vertical forces along axis Z, and transmission of the engine torque about axis X. The other transmits thrust and also lateral and vertical forces.
Generally a mounting means comprises a beam, optionally double, fixed to the pylon by bolts and joined to the engine case by links. These links swivel at their ends on devises or lugs, depending upon assembly, and are respectively integral with the case and beam. So that load transmission by the links is purely axial, a ball-joint bearing is provided for the cross pins, at each end of the links. With this assembly it is possible in particular to absorb radial and axial expansions of the engine. Provision is also made for connection means having a clearance, so-called standby connections, which become active when the clearance is reduced should one of the transmissions fail subsequent to failure of a part.
Patents EP 1216921 or FR 2820402 illustrate mounting modes of this type.
The beams are generally fairly massive and of complex shape. They ensure the transition between a horizontal plane of attachment to the pylon and a vertical plane comprising devises for connection to the engine. For wing mounting the height dimension of the beams depends upon the space that needs to be reserved for the attachment bolts to the pylon.
Also, a sufficient space must be set aside between the case and the beam to house the links and allow them free movement.
The attachment of the engines on some parts of the aircraft, for example on the wings, requires that the volume taken up by the mount should be as small as possible since the available space is fairly limited.